This invention relates to a rotary switch, more specifically to a rotary switch of the dual-in-line-package type (hereinafter called a DIP rotary switch).
A rotary switch having a "Dual-In-Line-Package" structure is small in size and has been developed for installation on a printed circuit board equipped with electronic appliances and control devices. Because the development of this type of switch has just recently started, only a few types are commercially available at present.
A DIP rotary switch of the prior art comprises a housing having a base made of insulative material through which several plate terminals are mounted in two rows, and further comprises a rotatable disc and a rotor with a rotator which are hermetically sealed within the housing. A projecting portion of the plate terminal positioned through a hole in the base is bent to form a reversed L-shaped contact segment while a downwardly protruding portion serves as a lead foot. Various patterns of conductive material devised to meet the desired purpose of the switch are arranged on the under surface of the disc which is positioned about a pivot in the base, the disc is simultaneously rotatable with the rotor.
With the rotation of the disc and the rotor, the conductive material of the disc may intermittently contact a contact point of the plate terminal arranged on the base, with resultant electrical connection or disconnection of the plate terminals arranged in two rows.
Because the DIP rotary switch of the conventional type is usually installed on a printed circuit board by the lead feet by means of a soldering process, careful attention must be paid to prevent an extra portion of solder or solder flux from flowing through the hole in the base and reaching the contact point thereby making the proper functioning of the switch unobtainable. It is also a common practice to clean the base and terminal assembly by washing with a solvent such as trichlene or Freon, and the same care must be taken to avoid the situation as explained above.
Therefore, to solve afore-mentioned problem, it is necessary to fix the lead foot of each plate terminal to the base hole so firmly and tightly that the flow of the extra material through the hole, as noted above, may be avoided.
Two methods have so far been adapted to avoid this problem. The first method is to tightly bond each lead foot to the base through a hole by applying an adhesive material therebetween, while the second method bonds each lead foot by means of an insert molding process.
However, bonding by means of an adhesive material lacks reliability because it is impossible to perform a satisfactory bonding of the two parts through a hole therebetween. This is also disadvantageous due to poor work efficiency because the plate terminals must be mounted to the base manually on a piece by piece basis.
In the insert molding method, plural plate terminals are simultaneously attached to the base by pouring plastic material into a mold where the plural plate terminals have already been positioned. Therefore, the disadvantage of poor work efficiency may be overcome.
However, a new problem may be created. The base should be arranged to allow the plate terminals to be firmly installed thereto. Therefore, the portion of the plate terminals held or sandwiched by the base must be long and the base must be thick enough to maintain a powerful bond between the plate terminal and the base. However, it is almost impossible to provide a length and thickness beyond a fixed limit due to the structural requirements of the switch, whereby a tight fastening of the plate terminals to the base may not be successfully obtained, with the resultant poor installation of the plate terminal to the printed circuit board.
The position that a plate terminal is usually bent to form a contact point must be selected and arranged with accuracy and efficiency. In this type of conventional switch, it is not an easy job to bend a contact point to be located at the right position with accuracy and efficiency. Usually, the plate terminals have already been manufactured before starting the molding process and they are manually arranged vertically in rows in a mold on a piece by piece basis so as to be ready for the molding process. Therefore, it is naturally difficult to maintain a uniform and firm installation of the plate terminals to the base. In addition, the components required for assembling such a small switch may considerably increase in number with the resultant disadvantages in quality control and work efficiency.
It is, therefore, an object of this invention to provide a DIP rotary switch which has plural plate terminals arranged to be connected and formed integrally as one flat piece, whereby each plate terminal is horizontally and firmly fastened to the base by means of an insert molding process.
Another object of the invention is to provide an improved DIP rotary switch which has a thin base and consists of a small number of components whereby the fastening of the plate terminals to the base may be performed efficiently by the process of molding.
A further object of the invention is to provide a DIP rotary switch whose base has hollows provided with steps at the edges of the surface and at the under surface thereof respectively, and has guide slots positioned at the surface thereof so that the bending of the plate terminals to form contact points and lead feet may be performed with high efficiency and accuracy.
An even further object of this invention is to provide a manufacturing process for the plate terminals and bases of DIP rotary switches.
The above and further objects and novel features of the invention will more fully appear from the following detailed description when read in connection with the accompanying drawings. It is to be expressly understood, however, that the drawings are for the purpose of illustration only and are not intended as a definition of the limits of the invention.